1. Field of the Invention
The present invention relates to an image forming apparatus that has a function of automatically selecting one of a plurality of sheet feeders, and more particularly to an image forming apparatus that is suitable for performing a sheet feeding operation as desired by a user, a method of controlling the image forming apparatus, and a storage medium storing a control program for implementing the method.
2. Related Art
In recent years, there has been developed a digital image forming apparatus that has an automatic sheet selecting function in which the size of a read original is determined and an optimum sheet feeding port is automatically selected according to the determined sheet size. In such an image forming apparatus with an automatic sheet selecting function, in the case where the optimum sheet feeding port is selected from a plurality of sheet feeding ports, when a switch for setting inhibition of selection of a sheet feeding port (hereinafter referred to as “selection-inhibiting switch”), provided in the image forming apparatus, is turned on, a sheet feeding port associated with the switch is excluded from sheet feeding ports to be selected.
In the digital image forming apparatus, it is required to set sheet types for the respective sheet feeding ports so that a user can confirm types of sheets stored in the sheet feeding ports when he inputs a desired sheet type for a specific sheet feeding port to carry out image formation and output the formed image. If sheets of an improper type are stored in association with the specific sheet feeding port, the user selects a different sheet feeding port to carry out image formation and output the formed image.
In the above conventional digital image forming apparatus, however, even if the sheet type has already been designated, if there is a sheet feeding port that can feed sheets of the same size as the sheet size input by the user and on which images are to be formed, the above sheet feeding port is automatically selected to feed sheets irrespective of the set sheet type. To exclude the sheets of the same size from sheets to be selected, the selection-inhibiting switch has to be turned on. To stop sheet feeding when a desired copying mode is not selected, the switch has to be reset.
In a digital composite apparatus (an apparatus having a plurality of functions such as an image reading function, an image forming function, and a facsimile function) having three sheet feeding ports, for example, when prepunched or colored paper, recycled paper and ordinary paper are stored in sheet feeding ports 1, 2 and 3, respectively, a sheet feeding port that feeds sheets of the same size as the sheet size input by the user is automatically selected in a mode in which a sheet feeding port is automatically selected, irrespective of the sheet type. For example, if the sheets stored in all the sheet feeding ports are of A4 size and the sheet size input by the user is also of A4 size, the sheet feeding port for prepunched paper can be automatically selected, even though he wishes to copy the original on ordinary paper.